A great deal of psychological research over the
last twenty years suggeststhat humans, like animals, are endowed with
an innate number system, andthat this system forms the basis for furthe
r counting and arithmeticskills. One line of evidence supporting
this view comes from infancyresearch. It turns out that infants c
an represent and perform operationson numerical information across a va
riety of experimental techniques (e.g.Sparky, Spelke & Gelman, 1990
, Wynn, 1992)

However, these infancy results have recently been chal
lenged by new dataindicating that infant discrete numerical competencie
s appear to breakdown when continuous quantities are controlled.
For example, inhabituation experiments, infants do not detect the diffe
rence between twocircles and three circles when the total area of the c
ombined circlesremains constant (Clearfield & Mix 2001.)

Whi
le this data has been used to discount continuity models of discretenum
ber, it can alternatively be an indicator that continuous and discreten
umber representations are processed automatically, and that one process
can interfere with the other. I will present adult response tim
e datathat supports this second proposal. Adults are unable to ig
noreirrelevant continuous quantity information when performing counting
tasks,and are unable to ignore number when performing tasks involving
continuousquantity. These data may explain some of th
e conflicting infancyresults, as well as offer further insight into the
way in which numericalinformation is processed on-line.